Electronic sensors and respective control units communicate, for example, over a bus system. To this end, data to be transmitted are coded as a binary signal which is generated on the data bus. There are several standards for such bus systems like Controller Area Network, CAN, Local Interconnect Network, LIN, or others.
For example, a LIN-bus can be used in automotive applications. It has a concept of a single master and multiple slaves connected to a single bus wire. The bus wire is electrically connected to the supply voltage which usually is positive with respect to a ground voltage by means of a pull-up resistor. The bus wire is kept in a recessive voltage level corresponding to a relatively high positive voltage near to the positive supply voltage by this pull-up resistor. Master and slave units usually comprise a built-in line driver for pulling down the voltage on the bus wire to a dominant voltage level corresponding to a relatively low positive voltage near to the ground voltage level in response to a data signal. According to the LIN standard, a respective LIN cluster can have up to sixteen slave units being connected to a master unit by the bus wire.
For bus systems, especially in automotive networks, there can be stringent requirements on the electromagnetic emissions of the output drivers generating the signal on the bus system. Fast rising or failing transients on the bus networks can be a major source of energy emission since they generate many high-frequency components. Turning on or off respective drivers instantly can result in undesirable overshoots or undershoots in supply and ground. Thus, these fast transitions can be a major source of electromagnetic emissions and, therefore, radio frequency disturbances on the bus wire. Such disturbances can result in misinterpretation of the recessive and dominant voltage levels on the bus wire.
Furthermore, an asymmetrical propagation delay between the rising and the falling edges of the bus signal can cause a duty cycle different from a usually desired value of 50%.
Both these issues can be a cause for faulty communication. To this end, some bus standards like the LIN standard determine ranges for duty cycles and propagation delays. Respective rise times and fall times of transitions between a recessive voltage level and a dominant voltage level or between a high and a low state, respectively, of a bus signal can be derived from these standard given values.
In conventional driver arrangements for such bus systems, the rise and fall times depend on the load of the bus wire which, for example, is determined by the number of communication units connected to the bus wire. Furthermore, such driver arrangements can be dependent on PVT variations, i.e. variations of process, voltage and temperature, regarding the rise and fall times.